Apparatus for generating a representation of the junction between two solids in a cathode ray tube display



Aug. 4, 1970 L. HARRISON Ill APPARATUS FOR GENERATING A REPRESENTATION OF THE JUNCTION BETWEEN TWO SOLIDS IN A CATHODE RAY TUBE DISPLAY 2 Sheets-Sheet 1 Filed Jan. 15, 1968 a 3 .m N- 5 I M Q mm p we mm mm mh w F55 wkqm m mtuw N mmkmi flv qwhu! QM 1Q m2 Qmk MEQWQQ mm Wmhmi (M mm W & S Q: .A.||\ I wq QM Wm QR 1% MO\ C as M Q 8 vm om m8 9 1/ No m0 N% m& m N: E w mm Ev I In W m m m: Q w 3 Tm w: v: 5 8 m mu A A o& m \i N E Q Q Q9 g k mt kw J QN\\ TL .v a 3 em 9v 2w av Q 3m fl Q Q mm mm mm X mm v wmkkbou kmkzbsu mmwuwq m qumd A @N. mm Fl 3 Aug. 4, 1970 L. HARRISON m 3,523,289

APPARATUS FOR GENERATING A REPRESENTATION OF THE JUNCTION BETWEEN TWO SOLIDS IN A CATHODE RAY TUBE DISPLAY Filed Jan. 15, 1968 2 Sheets-Sheet 2 Med 206 MASTER R5557 we I 756 A69 P 173.5 N U r 1 b ry 2oz 1 cow/r512 /?zm PULSE 21:; b //v/ ur MASTER wab 1741 2 i 193 P5357 111 182G m 1 1 9g 5% 205 R i p l\\\\ 051 W COUNTER I Z04? 2031 1 m 1924 194 Q8 1694 2034 g5 19? lA/VENTOI? LEE HHRRISOME United States Patent O 3,523,289 APPARATUS FOR GENERATING A REPRESENTA- TION OF THE JUNCTION BETWEEN TWO SOLIDS IN A CATHODE RAY TUBE DISPLAY Lee Harrison III, Englewood, Colo., assignor to Computer Image Corporation, Denver, Colo., a corporation of Delaware Continuation-impart of application Ser. No. 607,078, Jan. 3, 1967. This appplication Jan. 15, 1968, Ser. No. 698,017

Int. Cl. H01j 31/10 US. Cl. 340-324 9 Claims ABSTRACT OF THE DISCLOSURE A network for maintaining continuity of generated surfaces on members which are pivotally connected to gether in a display produced by an electronic image generator. Lengths of the numbers are programmed to a counter to automatically generate extensions of desig nated members beyond their pivotal connections to other members, enabling the surfaces of the pivotally connected members to maintain their continuity.

CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of application Ser. No. 607,078 filed Jan. 3, 1967, now Pat No. 3,364,382 and which was a continuation of application Ser. No. 240,970, filed Nov. 29, 1962, now abandoned.

BRIEF DESCRIPTION OF THE INVENTION The basic approach to electronically generating animated figures is as set forth in the Lee Harrison III application. That is, basic axial vectors (designated bone vectors) and volumetric vectors (designated skin vectors) are generated and combined to produce information defining the display subject in three dimensions, after which the three-dimensional information is transformed into any selected two-dimensional information for display or recording.

In many cases, the display subject of the Lee Harrison III application has individual members or bones joined together end to end, such as the members forming an arm (placement bone, upper arm bone, lower arm bone, and hand bone). Some of these bones are to be moved relative to one another. For example, the lower arm bone may be pivoted relative to the upper arm bone about the point where they are joined (the elbow) and motions of this kind are selectively established by varying the outputs of angular parameter gates that are opened to generate voltages corresponding to the angular positions of the basic axial vectors as the basic axial vectors are generated.

As the Lee Harrison III application describes, the volumetric or skin vector is generated as an amplitude modulated voltage which is sinusoidally added to the basic axial vector or bone vector in time sequence with the generation of the bone vector. The variations of amplitude of this skin vector correspond to the volumetric irregularities in the surface characteristics of the display subject or, in the electronic generation approach, the variations in distances of points on the surfaces of the figure from its basic axial vectors. Thus, the skin vector can be modulated to produce any desired skin shape.

Although the skin vector can be modulated, there are times when the skin on one bone may fail to meet the skin on an adjacent bone when the bones are pivoted relative to one another. This invention pro ice vides a network for maintaining continuity of the skin at the pivotal joints of adjacent bones.

The approach in this joint counter network is to designate certain bones as joint bones. A joint bone is one which has an end connected to the end of another bone that may pivot relative to the joint bone. Each bone that is designated a joint bone has certain connections to the joint control network.

The joint control network is to enable drawing a joint bone with an end that extends beyond the point where the next bone is pivotally connected. Modulated skin is added as the bone is drawn in the manner described in the Lee Harrison III application, so the joint bone and its volume or skin permit the pivoting bone and its skin to pivot as desired without separating the skin of the two bones. The skin on the extension of the joint can be shaped by modulating the volumetric or skin vector to establish smooth continuity between the skin on the joint bone and the skin on the next bone.

The joint control network has a designator counter input and a length counter input for each joint bone. It also has a joint counter and a flip-flop that can be toggled to deliver a signal to either an in bus or an out bus. (Reference to the Lee Harrison III application shows that members are generated in an out direction and in direction and that the drawing of each member is done in either the out or in direction, usually according to the angular position of the member relative to the selected two-dimensional viewing plane as related to the overlap prevention network.)

The joint counter establishes the length of the bone extension past the point of its pivotal connection to the next bone. The designator input establishes a total bone length equal to the length from end to end plus the length provided by the joint counter. The length counter input establishes the length of the bone, not including the count of the joint. Therefore, the length of the designator input is equal to the length of the length counter input plus the length of the joint counter.

For each joint bone, therefore, a counter establishes the duration during which the parameter gates are open, the parameter gates establishing the angular position of the bone (corresponding to the 6 and o gates of the Lee Harrison III application, with other gates for any other desired parameters, such as rotational position, intensity, etc.). The counter is set to correspond to a bone length as dictated by the designator input. In the out condition, the designator and length counter inputs begin transmitting signals with the start of the counter. When the counter has counted the length programmed for the length counter, a pulse is transmitted both to the joint counter and to a flip-flop which is toggled from the out to the in condition (a phase shift as described in the Lee Harrison III application). The joint counter then counts a length programmed for the particular joint bone in an in direction. When the joint counter completes its count, simultaneously with completion of the counting to the designator input, the joint counter is reset for a new count and the counting for the next bone begins.

The aforesaid Lee Harrison III application describes an arrangement of step counters for establishing bone lengths. A different network, incorporating a decade counter and a plurality of flip-flops, is provided by the present invention. The flip-flops control the opening of the parameter gates.

The logic which steers the start and stop pulses from one flip-flop to the next is the same as disclosed in the Lee Harrison III application. The change herein is that a single electronic counter is used to control the length of time that each of the flip-flops in the array is in the set condition. The type of counter used is more expensive than a single step counter but is much more accurate.

A single counter, referred to as a length counter, is used for all of the flip-flops. The counter is started at the beginning of any flip-flop cycle and is reset when the desired count for that flip-flop is reached.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the length counter network.

FIG. 2 is a schematic diagram of the joint control and turn-around control networks.

FIG. 3 is a diagrammatic view of a discontinuous surface that might occur Without the joint control network of this invention.

FIG. 4 is a diagrammatic view of the surface continuity that can be maintained with the joint control network of this invention.

DETAILED DESCRIPTION OF THE INVENTION In the joint control and counter network 30, there is a length counter 31 comprising any number of decade counters, two counters 32 and 33 being shown in this example. As is understood in the art, the first counter 32 has outputs 34, 35, 36 37, 38, 39, 40, 41, 42 and 43 corresponding to zero to nine counts, respectively, and the second counter has outputs 44, 45, 46, 47, 48, 49, 50, 51 and 52 corresponding to ten, twenty, thirty, forty, fifty, sixty, seventy, eighty and ninety counts, respectively. An input conductor 53 to the counter 32 supplies a high frequency square wave to be counted. Another input conductor 54 to the counter 31 is connected to the output of an or gate 55 to reset the counter 31 as will appear.

In the example, illustrated there are controls and gates for four bones, each having a flip-flop. Therefore, there are four gate-control flip-flops 57, 58, 59 and 60. The flip-flops 57, 58, 59 and 60 have set output conductors 61, 62, 63 and 64 leading to their respective parameter groups of gates 65, 66, 67 and 68. Each group of parameter gates 68 corresponds to the 0, r, and i gates associated with each bone such as the gates 69, 70, 71 and 72 of the aforesaid Lee Harrison III application, together with such other gates as may be desired. There is a group of such gates associated with the output from each flipfiop 57, 58, 59 and 60.

A set input conductor 72 to the flip-flop 57 is connected from an or gate 73. The or gate 73 has two input conductors 74 and 75. In this example, the flipfiop 57 corresponds to the first bone to be drawn; therefore, the input conductor 74 is plugged to a conductor 56 carrying a start or frame pulse, such as the frame-pulsecarrying conductor 41N of the aforesaid Lee Harrison III application.

There is a reset input conductor 76 connected from the output of an and gate 77. One input conductor 78 to the and gate 77 is connected from the set output conductor 61 from the flip-flop 57. Other input conductors 79 and 80 are connected to plugs of the length counter 31 corresponding to the desired length of the bone with which the flip-flop 57 is associated. In this example, the connections 35 and 44 correspond to a counter length of 11.

A plug 82 is connected to the output conductor 61 from the flip-flop 57 to enable any desired designation of the bone corresponding to the flip-flop 57 as may be desired and as will be described hereinafter. Also, a conductor 83 is connected to the set output conductor 61 and to two conductors 84 and 85 that connect it to the differentiator inputs of two and gates 86 and 87. Another input conductor 88 to the differentiator and gate 86 is connected to an out bus 89. Another input conductor 90 to the differentiator and gate 87 is connected to an in bus 91.

An output plug 93 from the gate 86 is, in the example illustrated, plugged to a conductor 94 leading to an or gate 95. An output conductor 96 from the or gate is connected to the set input to the flip-flop 58. There is also an output plug 97 associated with the gate 87.

An input conductor 98 to the reset input of the flipfiop 58 is connected to the output from an and gate 99. One input conductor 100 to the and gate 99 is connected from the set output conductor 62 from the flipflop 58, and another input conductor 101 is connected to the programmed count for the bone associated with the flip-flop 58, in this case the counter output 40.

There is a designator plug 103 connected to the set output conductor 62 and a conductor 104 having conductors 105 and 106 connected to the differentiator inputs to two differentiator inputs to two difierentiator and gates 107 and 108. A conductor 109 connected from the out bus 89 provides another input to the difierentiator and gate 107, and a conductor 110 connected from the in bus 91 provides another input to the differentiator and gate 108. There are output conductor plugs 111 and 112 leading from the gates 107 and 108. In this example, the plug 111 is connected to an input conductor 113 to an or gate 114 and the plug 112 is connected to the input conductor 75 to the or gate 73 on the set input side of the flip-flop 57.

An output conductor 118 from the or gate 114 leads to the set input to the flip-flop 59. A conductor 119 to the reset input of the flip-flop 59 is connected to the output from an and gate 120. One input conductor 121 to the and gate is connected to the set output conductor 63. Other input conductors 122 and 123 are connected to the counter outputs 40 and 44 to provide a sixteen length count for the particular bone associated with the flip-flop 59. There is a designator plug 125 connected to the output conductor 63 and, since the bone associated with the flip-flop 59, in this example, has been designated a joint bone, there is a conductor 126 plugged to the designator plug 125, and the seventeen count program for the flipflop 59 corresponds to the designator input count and functions as will be described.

A conductor 128 leads from the set output conductor 63 to two conductors 129 and 130 connected to the differentiator inputs of a pair of differentiator and gates 131 and 132. A conductor 133 connected from the out bus 89 provides another input for the gate 131, and a conductor 134 leading from the in bus 91 provides another input to the gate 132. An output plug 136 is connected to the output of the gate 131, and in this example, is plugged to an input conductor 137 to an or gate 138. An output plug 139 connected to the output from the gate 132 is connected by a conductor 140 into the or gate 96.

An output conductor 143 from the or gate 138 is connected to the set input of the flip-flop 60. A conductor 144 leading from an and gate 145 is connected to the reset input of the flip-flop 60. One input conductor 146 to the and gate 145 is connected from the set output conductor 64. Another input conductor 147 to the and gate 145 is connected to the output 45 from the counter 33 corresponding to a twenty count.

A designator plug 149 is connected to the set output conductor 64. In this example, the bone corresponding to the flip-flop 60 has been designated a turn-around bone, and therefore, there is a conductor 150 plugged to the plug 149, and the twenty count for the flip-flop 60 is double the length of the bone. The connections of the conductor 150 to the turn-around control will be described hereinafter.

A conductor 152 leading from the set output con ductor 64 is connected to input conductors 153 and 154 to the differentiator inputs of a pair of differentiator and gates 155 and 156, the other input conductors 157 and 158 being connected to the out bus 89 and in bus 91, respectively. There is an output plug 159 connected to the output from the gate 155 and an output plug 160 connected to the output from the gate 156. In this example, no conductor is connected to the output plug 159. A conductor 161 is connected to the output plug 160 and to the or gate 114.

Joint control and turn-around control connections will now be described. The joint control network and turnaround control network each have duplicate connections for bones designated joint control or turn-around so connections in each network will first be described for a single joint control bone and a single turn-around bone.

As has been said, the bone corresponding to the flipfiop 59 has been designated a joint bone, and therefore a conductor 126 connected to the designator plug 125 is plugged to a designator input plug 169 of a joint control network 170. There are two and gates 171 and 172 associated with each joint bone. One of the and gates 171 has an input conductor 173 connected from the in bus 91. The other and gate 172 has an input conductor 174 connected to the out bus 89. Another input conductor 175 to the and gate 171 is connected to the designator plug 169, and an input conductor 176 to the and gate 172 is connected to the designator plug 169. Another input conductor 177 to the and gate 171 is plugged to the zero pulse output conductor 34 of the counter 31. Input conductors 178 and 179 to the and gate 172 are plugged to the selected ones of the counter outputs corresponding to the true length of the joint bone, in this example, the outputs 38 and 44 corresponding to a l4-count length.

There are output conductors 182 and 183 leading from the and gates 171 and 172 to an or gate 184. An output conductor 185 from the or gate 184 leads to another or gate 186 that has a conductor 187 leading from it to toggle an in-out flip-flop 188. One output conductor 189 from the flip-flop is connected to the out bus 89. The other output conductor 190 from the flipflop 188 is connected to the in bus 91. The output conductor 185 from the or gate 184 is also connected by a conductor 192 to the set input of a joint counter 193 that can be made to count any number of counts for the extension of a joint bone. In the example illustrated, the joint counter is shown with five output plugs 194, 195, 196, 197 and 198 corresponding to counts 1, 2, 3, 4, and 5, respectively.

There is a reset input conductor 200 leading to the joint counter 193 from the output of an or gate 201. An input conductor 202 to the or gate 201 is connected from the output of an and gate 203. One input conductor 204 to the and gate 203 is connected to the designated counter input 169. Another input 205 to the and gate 203, constitutes a plug into which a conductor 206 from the joint counter output may be connected. In the example illustrated, the conductor 206 is connected to the output plug 196 of the joint counter 193 corresponding to a 3-count. Another conductor 207 is connected from the output of the or gate 201 to the or gate 186.

The turn-around control 210 comprises an and gate 211 having an output conductor 212 connected as an input to the or gate 186 on the input side of the in-out flip-flop 188. There are two plugs 213 and 214 connected as inputs to the and gate 211. One of these plugs 213 is connected to the designator plug of a flip-flop that corresponds to a turn-around bone. In this example, the plug 213 is connected by a conductor 215 to the designator plug 149 on the output side of the flip-flop 60. The other plug 214 is connected by a conductor 216 to the output plug 44 corresponding to a -count, representing the true length of the bone, being one-half the count of the flip-flop 60.

While the foregoing describes connections for one joint control bone and one turn-around bone, the joint control and turn-around networks may incorporate connections for any desired number of joint control and turnaround bones. FIG. 2 shows such connections for five joint control bones and five turn-around bones, wherein subscripts a, b, c and d have been used with numbers which refer to comparts, for bones similar to the connections already described for one joint control bone and one turn-around bone.

OPERATION Before operating the system, various connections are made according to the determination of lengths of the physical members and according to which ones are to be designated join bones and which ones are to be designated turn-around bones. Also, connections are made according to the order in which the physical members are to be drawn. In this example, it is assumed that the desired order of operation begins with the bone corresponding to the flip-flop 57 followed in order by the bones corresponding to the flip-flops 58, 59, and 60. Therefore, the output plug 93 from the difi'erentiator and gate 86 is connected to the or gate 95, the output plug 111 from the differentiator and gate 107 is connected to the or gate 114, the output plug 136 from the diiferentiator and gate 131 is connected to the or gate 138, the output plug 160 from the difi'erentiator and gate 156 is connected to the or gate 114, the output plug 131 from the differentiator and gate 132 is connected to the or gate 95, and the output plug 97 is connected to the or gate on the input side of a flip-flop :for the next member group of flip-flop similar to those illustrated but for another series of physical parts of the display.

Also, in the example illustrated, the bone corresponding to the flip-flop 57 has been designated as a regular bone with a length corresponding to an 11-count, so there is no connection to the designator output plug 82 and the conductors 79 and are connected to the counter outputs 34 and 44 corresponding to an ll-count. The bone corresponding to the flip-flop 58 has also been designated a regular bone, so there is no conductor connected to the designator output 103 and the input conductor 101 has been connected to the counter output 40 corresponding to a length count of six. The bone corresponding to the flip-flop 59 has been designated a joint control bone with an actual length corresponding to a count of 14, and a joint length (the length of the extension of the bone beyond its pivotal connection to the next bone) has been determined to correspond to a joint count of three. Therefore, the total count for the length of the bone corresponding to the flip-flop 59 being the sum of 14+3, the conductors 122 and 123 are connected to the counter outputs 41 and 44 corresponding to a count of 17. Also, the designator plug is connected by the conductor 126 to the plug 169 of the joint control network 170.

The bone corresponding to the flip-flop 60 has been designated a turn-around bone. Therefore, the designator output 149 has been connected by a conductor to the plug 213 of the turn-around control 210. Since the true length of the bone corresponding to the flip-flop 60 has been determined to correspond to a count of ten, the conductor 147 is connected to the counter output 45 corresponding to a 20-count, or double the true length of the bone.

The system starts when a start signal from the conductor 41N passes through the or gate 73 to the start input conductor 72 connected to the flip-flop 57. The same start signal is conducted by the conductor 72 to the or gate 55 and the conductor 54 to reset the counter 31 to a zero count to start a new count. Upon flipping the flip-flop 57 to the set condition, an output signal from the set output conductor 61 is transmitted through the conductor 78 to the and gate 77 enabling the and gate 77 to receive counter signals from its conductors 79 and 80. The counter 31 having been reset by the signal in the conductor 54, it performs its counting operation of the square wave pulses delivered to it by the input conductor 53.

While the counter is counting to a total count of 11, as programmed to the flip-flop 57, the flipflop remains in set condition, but when the count of 11 is reached, signals are transmitted through both the conductors 79 and 80 to the and gate 77 joining the signal from the conductor 78 in the and gate 74 to pass a signal to the reset conductor 76 and reset the flip-flop to its reset condition. While the flip-flop 57 is in its set condition, the output conductor 61 enables its parameter gates 65 to pass voltages corresponding to the parameters for the bones with which the flip-flop 57 is associated. Thus, the location of the bone is determined and the skin is added to the bone, etc., all as described in the aforesaid Lee Harrison III application.

Upon resetting the flip-flop 57 to its reset condition, there is no longer a signal in the set output conductor 61. Therefore, there is a voltage change in the conductors 84 and 85 leading to the differentiator inputs of the differentiator and gates 86 and 87. Since the in-out flipflop 188 is toggled to the out condition, the out bus 89 carries a signal and the in buss 91 carries no signal. Therefore, the gate 87 does not pass a signal, but the gate 86 does pass a signal to the or gate 96 and the conductor 97. The signal in the conductor 97 is transmitted to the set input of the flip-flop 58 and to the or gate 55 to reset the counter 31.

Operation of the flip-flop 58 with its various connections is as described for the flip-flop 57 and, upon completion of this operation, a signal is transmitted to the conductor 113 to the or gate 114. This signal sets the flip-flop 59 in its set condition and also resets the counter 31.

The flip-flop 59 has been designated as one corresponding to a joint bone. When it is in its set condition, its parameter gates 67 are operated just like the other parameter gates 65 and 66. However, when the counter reaches a count of 14, there are signals in the conductors 178 and 179 connected to the and gate 172. Likewise, while the counter 31 is counting, there is a signal in the conductor 126 connected to the designator plug 125 and to the and gate 172 (as well as the and gate 171). Since the and gate 172 is connected by the conductor 174 to the out bus 89, it is the one that is enabled when the pulses from the fourteen-count output plugs 38 and 44 are transmitted to the and gate 172. This causes a signal to be transmitted through the conductor 183, the or gate 184, the conductor 185, and the or gate 185 simultaneously to the flip-flop 188 to toggle it from its set condition to its reset condition and, through the conductor 192, to the joint counter 193 to flip the joint counter to a set condition and start a joint count.

Since the flip-flop 188 has been flipped from set to reset, there is no longer a signal in the out bus 89 and instead, there is a signal in the in bus 91. Therefore, as the joint counter counts, and as the counter 31 continues to count and hold the flip-flop 59 in its set condition, the drawing is shifted 180 to draw in rather than out for a bone length corresponding to a three count as programmed by the connection to the output 196 of the joint counter 193.

When the joint counter reaches a three count, a signal is transmitted through the conductor 206 to the and gate 203, which, at the same time, has a signal in the conductor 204. This enables the signal to be sent through the conductor 202, the or gate 201, and the conductor 200 to reset the joint counter 193. The same signal is also sent through the conductor 207 and the or gate 186 to toggle the flip-flop 188 to the set or out condition. Simultaneously, the counter 31 reaches the seventeen count programmed for the flip-flop 59, and the flipfiop is flipped to its reset state, sending a pulse to the conductor 129, the gate 313, and the or gate 138 to the flip-flop 60.

The flip-flop 60 has been designated as one corresponding to a turn-around bone. Therefore, when the flipflop 60 is flipped to its set condition, a signal is transmitted through the conductor 215 to the and gate 211. When the counter reaches a count of ten, there is also a pulse in the conductor 216 to the and gate 211, and this pulse is transmitted to the or gate 186 and the conductor 187 to flip the flip-flop 188 to its reset state. This puts a signal in the in the bus 91 rather than the out bus 89, so that the direction of drawing the member is reversed.

When the flip-flop 60 is flipped to its reset" state upon the counter 31 reaching the twenty count a signal is transmitted through the conductor 161 to the or gate 114, causing the flipflop 59 to operate again as before described, except now, the flip-flop 188 has not been toggled from reset to set. Hence, when the drawing of the joint bone has been completed and the flip-flop 59 is reset, there is an output signal through the diflerentiator and gate 132 by the conductor to the or gate 96. In this manner, the flip-flop 58 is operated, followed by the flip-flop 57 to complete drawing the members in the in condition. After the flip-flop 57 has again operated, a signal is transmitted through the gate 87 to the plug 97 to be carried to the next member group for a similar operation. At the same time a signal is sent by appropriate conductors (not shown) to reset all flip-flops in their original conditions.

FIGS. 3 and 4 illustrate the results of using the joint control network of this invention. In FIG. 3, there is no joint control for drawing an arm 220 with a placement bone 221, an upper arm bone 222, a lower arm bone 223, and a hand bone 224. The upper arm, lower arm, and hand bones have skin surfaces 225, 226, and 227, respectively. Since, as described in the aforesaid Lee Harrison III application, only the skin or surfaces 225, 226, and 227 are drawn, the bones 221, 222, 223, and 224 are shown in dotted lines. FIG. 3 shows how the surfaces 225 and 226 may part at the elbow when the lower arm is pivoted relative to the upper arm.

In FIG. 4, an arm 230 has a placement bone 231, a joint bone comprising an upper arm bone 232 With an extension 233, a lower arm bone 234, and a hand bone 225, the latter also being a turn-around bone. The upper arm bone 232 has a surface 236, including a surface 237 on the extension. The lower arm and hand bones 234 and 235 also have surfaces 238 and 239. The surface 237 on the extension of the joint bone 232 is properly shaped to maintain continuity of skin at the elbow.

What is claimed is:

1. A network for interconnecting surfaces on pivotally connected members of a display produced by an electronic image generator, wherein each member has a reference axis, comprising means to generate parameter voltages representing the position of each member in three-dimensional space, means to time the duration of the generated parameter voltages in proportion to the lengths of the members, means to sequence the generating means such that the generation of voltages corresponding to a first member of the display is followed by the generation of voltages corresponding to a second member of the display with an end of the second member being joined to the first member at the intersection of the reference axes of the two members, and means to generate extension parameter voltages corresponding to an extension of the first member beyond the said point of intersection.

2. The network of claim 1 including means to control the duration of the last-named generator means in proportion to the length of the said extension.

3. The network of claim 1 wherein the parameter voltage generator includes means to alternately generate voltages corresponding to drawing the members away from or toward an end of the first member.

4. The network of claim 1 wherein the parameter voltage generator comprises a control valve means for each member, each control valve means having a first state and a second state, a plurality of parameter gates opened for the duration of the first state of each control valve means, pulse counter means for establishing the duration of the said first state of each control valve means in response to the number of pulses counted by the counter means, and means to provide a parameter voltage from each gate for the duration it is open, each parameter voltage being selectively variable according to the desired position of a member of the display.

5. The network of claim 2 including means to automatically control the program means in response to operation of the extension parameter voltage generator.

6. The network of claim 5 wherein the automatic control means comprises a flip-flop triggered by a start and a stop signal at the beginning and end of operation of the extension parameter voltage generator.

7. The network of claim 3 including means to control the program means to reverse the correspondence of voltages generated according to a pre-determined programmed designation of a member.

8. In an electronic image generator having means to generate visual representations of signals corresponding to a display subject wherein the display subject has a plurality of members joined together and each member has a reference axis and a surface spaced from the reference axis, means to generate signals to establish the length of the axis of a first member, means responsive to generation of length signals to generate parametric signals to define the position of the first member, means to automatically repeat the length signal for a predetermined duration while simultaneously reversing the parametric signals to create an extension of the first member beyond a juncture point, and means to generate length signals and means to generate parametric signals corresponding to the length and position of the axis of a second member joined to the first member at the juncture point of the first member.

9. The combination of claim 8 including means to automatically reverse the generation of signals defining the plurality of members following completion of a sequence of generation thereof.

References Cited UNITED STATES PATENTS 2,578,970 12/ 195 1 Gannaway 340-324.1 2,877,457 3/ 1959 Gimpel 340-324.1 2,980,332 4/1961 Brouillette 235-189 JOHN W. CALDWELL, Primary Examiner M. M. CURTIS, Assistant Examiner US. Cl. X.R. 

